1. Field of the Invention
The present invention relates to a sound reproducing apparatus, and more particularly to a sound reproducing apparatus having a display means and being capable of acoustically driving a transparent diaphragm panel.
2. Description of the Background Art
Conventionally, there has been devised a sound reproducing apparatus for reproducing sound from a display screen. For example, there exists a sound reproducing apparatus which causes a transparent diaphragm panel provided in front of a display screen to vibrate to emit sound. This sound reproducing apparatus will be described below with reference to FIG. 11.
FIG. 11 is an external perspective view of a television set having a conventional sound reproducing apparatus. In FIG. 11, the television set includes a cabinet 1, a cathode ray tube 2, a front panel 3, a driver 4, and sound slits 5. The front panel 3 is mounted in front of the cathode ray tube 2. The front panel 3 is composed of a material with high optical transmittance, such as glass or transparent acrylic. The driver 4 is an electromagnetic-type speaker and is directly connected to the back of the front panel 3. A plurality of sound slits 5 (four sound slits in FIG. 11) are provided around the perimeter of the cathode ray tube 2. The television set shown in FIG. 11 reproduces sound by a method of directly driving the transparent diaphragm panel by means of the driver 4.
The operation of the sound reproducing apparatus shown in FIG. 11 will be described below. When an electrical signal is applied to the driver 4, the driver 4 causes vibration. Since the driver 4 is directly mounted to the front panel 3, the vibration caused by the driver 4 is mechanically transmitted to the front panel 3, causing the front panel 3 to vibrate. Specifically, if the electrical signal applied to the driver 4 is an audio signal, sound is reproduced from the front panel 3 mounted in front of the cathode ray tube 2. Since the front panel 3 is composed of a material with high optical transmittance, the front panel 3 does not degrade an image reproduced on the cathode ray tube 2. In this manner, the television set shown in FIG. 11 can simultaneously reproduce images and sounds.
If the volume of a space between the front panel 3 and the cathode ray tube 2 is small, the air pressure of the space will increase, whereby the limit of low-frequency sound reproduction in sound reproduction is increased. In order to prevent this problem, the sound slits 5 are provided. Specifically, sound coming from the back of the front panel 3 passes through the sound slits 5 and then is emitted into the cabinet 1. Thus, an increase in the air pressure of the space can be avoided by means of the sound slits 5.
While the sound reproducing apparatus shown in FIG. 11 is used as a television set, there also exists a sound reproducing apparatus which can be used as a mobile telephone. Such a sound reproducing apparatus reproduces sound by causing an outer case which is directly mounted to the mobile telephone to vibrate by means of the driver. This sound reproducing apparatus will be described below with reference to FIG. 12.
FIG. 12 is an external view of a mobile telephone having a conventional sound reproducing apparatus. In FIG. 12, the mobile telephone includes an outer case 10, an antenna 11, a soundboard 12, a driver 13, and a display screen 14. The soundboard 12 is formed on the upper front of the outer case 10 such that the perimeter thereof is thin (not shown). The driver 13 is directly mounted to the back of the soundboard 12. The display screen 14 is provided on the front of the outer case 10 and below the soundboard 12.
The operation of the sound reproducing apparatus shown in FIG. 12 will be described below. When an electrical signal is applied to the driver 13, the driver 13 causes vibration. The vibration caused by the driver 13 is directly transmitted to the soundboard 12 formed on the outer case 10, causing the soundboard 12 to vibrate, thereby reproducing sound.
In the sound reproducing apparatus shown in FIG. 11, the driver 4 is mounted in a location around the perimeter of the front panel 3 so as not to block the display screen of the cathode ray tube 2. On the other hand, in a sound reproducing apparatus which employs a method for directly driving the font panel 3 by means of the driver 4, if the driver 4 is mounted in a location around the perimeter of the front panel 3, the quality of reproduced sound may be degraded.
Moreover, since the front panel 3 acts not only as a diaphragm panel for emitting sound but also as a protection panel for protecting the cathode ray tube 2, the front panel 3 requires moderate strength. Therefore, the front panel 3 needs to be configured to have a certain thickness. This increases the weight of the front panel 3, reducing the vibration of the front panel 3 brought about by the driver 4, resulting in a reduction in reproduced sound pressure. Thus, in the sound reproducing apparatus shown in FIG. 11, the efficiency of the reproduced sound pressure with respect to the driver is very low as compared with that of conventional speakers.
The sound reproducing apparatus shown in FIG. 12, on the hand, cannot be appropriately applied to recent mobile telephones in which larger display screens are highly demanded. Specifically, in the sound reproducing apparatus shown in FIG. 12, the display screen 14 and the soundboard 12 are provided in different locations, which hinders the formation of a larger display screen 14 due to the presence of the soundboard 12. In addition, since the display screen 14 is provided in a different location from where sound is reproduced, the user cannot get the sense that the sound is being reproduced from the display screen 14.